<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>循环</title>
</head>
<body>
    <!-- 打印0-20之间的整数, 将每个数输出到控制台 -->
     <script>
        for(let a =0;a<=20;a++){
            console.log(a)
        }
     </script>
</body>
</html>